Spectrums are very valuable resources in wireless communications. An existing communications system usually works on a carrier frequency below 3 GHz. With emergence of smart terminals, particularly video services, current spectrum resources are difficult to meet an explosively growing user demand for capacity. A high frequency band with a larger available bandwidth, particularly a millimeter-wave band, gradually becomes a candidate frequency band of a next generation communications system.
Another advantage of using the high frequency band may be greatly reducing a size of multiple-antenna configuration, thereby facilitating site obtaining and deployment of more antennas. However, different from an operating band in a current system such as an LTE system, the high frequency band results in a relatively large path loss. Particularly, impact factors such as atmosphere and vegetation further increase a radio propagation loss.
For example, for transmission of a downlink common channel or a common reference signal, to overcome the relatively large propagation loss, a common-channel/common-signal transmission mechanism based on a beamforming technology is introduced, to obtain a relatively large antenna gain, so as to compensate for the loss in a common-channel/common-signal propagation process.
When transmission of the common channel (such as a broadcast channel, a synchronization signal, or system information) is based on the beamforming technology, a terminal device needs to separately demodulate a plurality of pieces of received system information, and this manner may result in unnecessary repeated demodulation by the terminal device. In addition, when user equipment is between two formed beams, demodulation based solely on system information received one time may result in unsatisfactory demodulation performance.